CO2 capture by solid sorbent can be realized by processes such as thermal swing, pressure swing, or vacuum swing. Due to the large quantity of CO2 released from coal fire plants, a large amount of sorbent is generally needed for CO2 capture. A honeycomb structure sorbent bed may solve the high pressure drop problem for fixed bed adsorption using a large amount of sorbent; but uniform and fast heating and cooling of the sorbent bed is still a challenge.
In CO2 solid sorbent capture, known processes mentioned above involve two steps: adsorption and desorption (or regeneration); and known processes involve sorbent bed temperature change. In thermal swing adsorption (TSA) processes, the sorbent adsorbs at a lower temperature and is then heated for desorption; after the desorption, the sorbent needs to be cooled down to a lower temperature for adsorption again. For vacuum and pressure swing adsorption (VSA and PSA) processes, the adsorption, an exothermal process, is accompanied with an temperature increase of the sorbent bed, which eventually prohibits the adsorption, or in other words, decreases the sorbent CO2 capacity; while the desorption, an endothermal process, is accompanied with a decrease of the sorbent bed temperature, and therefore, slows down the desorption process.